There are many different causes behind Arnold-Chiari malformations and nearly all have associated disorders. Chiari malformations occur due to structure-related defects in the spinal cord and the brain. Usually, these defects occur while the foetus is growing in the womb and which can occur due to low-nutrient intake during pregnancy or genetic mutations. Sometimes, the malformations occur later in life. This late onset happens due to injury, infection or exposure to toxic substances, which result in too much cerebrospinal fluid draining out from the thoracic or lumbar region. Usually, congenital Arnold-Chiari malformations are more common compared to late occurrences.
When the child is born with an Arnold-Chiari malformation or develops it later in life, there could be many disorders associated with the condition. The extent of these would be dependent on the severity of the condition. Some of the associated disorders include:
This is a condition that surfaces when the cerebrospinal fluid accumulates within the brain. Under normal circumstances, the fluid flows unobstructed from and to the brain. However, when this flow is blocked due to the malformation, it causes the fluid to buildup which exerts pressure within the brain. This can cause the skull to enlarge or get misshaped; it also can result in mental defects. If the hydrocephalus condition is severe and not treated in time, it can be fatal. While hydrocephalus can occur in any type of Arnold-Chiari malformation, it is seen more commonly in patients with Type II form of the syndrome.
Also referred to as hydromyelia, syringomyelia occurs when a tubular cyst forms inside the central canal of the spinal cord. This cyst is filled with cerebrospinal fluid, known as syrinx. As the cyst grows in size, it destroys the middle part of the spinal cord, causing the person to experience pain, weakness and stiffness in the arms, legs, shoulders and/or back. In addition, the person experiences headaches and the inability to feel extreme coldness or heat, particularly in the upper limbs. Some people suffering from syringomyelia can also experience excruciating pain in the arms and the neck.
This is a disorder wherein the spinal cord or the covering protecting it does not develop completely. Basically, when an infant is born with spina bifida, the bones covering the spinal cord do not form the right way and this leaves a part of the spinal cord exposed, causing partial or full paralysis. Usually, infants suffering from Type II Arnold-Chiari malformation have a form of spina bifida known as myelomeningocoele. In this type of spina bifida, the bones in the lower and back spine do not develop properly and end up protruding out of the back through an opening like a sac.
With people suffering from Arnold-Chiari malformation, sometimes the spinal cord gets connected to the bony spine. As a result, the spinal cord stretches abnormally. This disorder can result in permanent damage of the nerves, the muscles of the legs and the lower part of the body. Usually, kids diagnosed with myelomeningocoele have a higher risk of getting tethered cord syndrome as they grow older.
Those suffering from Type I form of Arnold Chiari malformation and syringomyelia tend to have a spinal curvature. This condition is known as scoliosis wherein the spine is bent either to the right or left, or bent forward (kyphosis).
Besides these associated disorders, those suffering from Arnold-Chiari malformations have certain skeletal and neurological abnormalities. They could have some other disorders that have an effect on the formation as well as the growth of the bones.